Letter S

The Definition of Shell Casing

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Shell Casing

A hollow, piece of metal (or plastic in the case of a shotgun shell) that is closed on one end except for a small hole which holds a primer. The open end holds the bullet. The hollow portion holds the powder. Together the assembled unit is called a cartridge.


19 Other Firearms Definitions You Need To Know


Annulus

A tiny circular recess at the base of a cartridge case surrounding the primer pocket. Recoil from fired cartridges invariably impress a discernable ring on the breech or bolt face of a firearm, providing some evidence of the amount of use it has seen.

Shotgun Shell

The cartridge for a shotgun. It is also called a "shell," and its body is usually made of plastic (metal shotgun shells are very rare, paper shotgun shells are extinct) with a metal head. Small shotshells are also made for rifles and handguns and are often used for vermin control.

Trigger Group

The entire collection of moving parts which work together to fire the gun when the trigger is pulled. It may include trigger springs, return springs, the trigger itself, the sear, disconnectors, and other parts.

Closed Bolt Firing System

A type of firearm in which the action is closed, with a cartridge in the chamber prior to firing. When the trigger is pressed the cartridge is fired, and the action cycles loading another cartridge into chamber and when firing is stopped the bolt remains closed and the chamber remains loaded.

Backstop

Anything that will safely stop a bullet and prevent it from hitting anything else after the target is struck.

Trap

A game of competitive clay pigeon shooting on a formally designed layout. In plan view, one launching machine is located 16 yards in front of a straight line, firing rising targets perpendicular to and away from that line. Five competitors shoot five individual targets at each of five stations along that line. Although each target is presented at slightly randomized vectors, trap emphasizes generally a single type of shot, outgoing and rising, and targets are broken at generally longer ranges than Skeet.

Single Action

An action type that when the trigger is pulled, the only thing the trigger does is drop the hammer (or striker). This applies to both revolvers, semi-automatic and automatic guns. On a single action revolver, the gun must be manually cocked before it can be fired. With semi-automatic and automatic guns that are single action, the only thing the trigger does is drop the hammer, striker or firing pin onto the cartridge. Then the firearm is cocked again when from the recoil of the fired round. A firearm that the gun is cocked and the hammer drops when the trigger is pulled is a double action gun.

Clicks

A unit of adjustment for a sight.

Scope Blocks

A pair of small dovetailed steel bases, screwed usually one to the barrel and one to the front receiver ring of a rifle, to accept mounts for target scopes such as the Unertl where the scope is allowed to move forward in the rings under the recoil of the rifle and which typically carry the windage and elevation adjustments in the mount.

Breech Pressure

The amount of rearward force exerted by the propellant gases on the bolt or breech of a firearm action or breech when a projectile is fired. The applied force has both magnitude and direction, making it a vector quantity. This is also known as Bolt Thrust on firearms that are Bolt Action

Cut-Away

A firearm that has had numerous careful machining cuts taken in its exterior with a view to exposing and demonstrating the functioning of critical parts of its mechanism

Muzzleloader

The earliest type of gun, now also popular as modern-made replicas, in which blackpowder and projectile(s) are separately loaded in through the muzzle. The term is often applied to cap-and-ball revolvers where the loading is done not actually through the muzzle but through the open ends of the cylinder's chambers.

Bottlenecked (Bottle Necked)

A type of cartridge whose bullet diameter is substantially less than the body diameter of the casing.

Mouse Gun

A name for any palm sized handgun which fires a small caliber.

Intercepting Sear

A second sear, poised just behind a second notch in the hammer. It is possible that when a cocked firearm is dropped or sharply jarred, a single sear could jump out of its notch and the hammer could fall, firing the gun accidentally. In this event, an intercepting sear would engage before the hammer could fall completely, preventing an accidental discharge. On a gun with intercepting sears, only by pulling the trigger are both sears moved out of the way simultaneously, allowing the gun to fire. Intercepting sears are usually found on better sidelock actions. They are sometimes found on best boxlocks, and can be recognized by an extra screw behind the action fences, in addition to the usual two screws (or pins) along the lower rear of the receiver.

Holdopen Toplever

A catch built into the receiver of a break-open gun to keep the toplever in its extreme right position when the barrels are removed. This device makes it slightly easier to remount the barrels. As the barrels are mounted and the breech closed, the barrels contact some kind of release pin (marked with the arrow) and the toplever automatically returns to the center locked position. Because, however, it requires a separate act to find and to depress this tiny tab to re-center the toplever on a broken-down gun, this feature may be irritating when trying to put a gun away in its case.

Spotter

The spotter is a helper who gives the shooter guidance on how to hit a particular target. In some cases the spotter may just report the location of the bullet impact. In other cases they may judge the speed and direction of the wind, determine the range, and give the shooter the settings to be used on the sights.

Hammerless

A firearm with a coil-spring-actuated firing pin, or with its hammer enclosed inside the action body; i.e.. no externally visible hammer.

Dram

A unit of measure traditionally used for black powder shotgun charges. Today, used for smokeless powders on the basis of the new propellant's equivalent performance to that weight of black powder. Thus, a shotgun shell marked 3 - 1 1/8 would be loaded with the smokeless powder equivalent of 3 drams of black powder, and with 1 ounce of shot. 1 Dram = 1/16 ounce = 437.5 grains.